In sport, Oscar Pistorius demonstrated how easy it is to be wrong about people. An athlete with prosthetic limbs competing at the Olympic Games? No way!
That lesson - don't leap to hasty, ill-informed conclusions - is worth remembering now as the double-amputee Olympian stands charged with murder in the shooting of his girlfriend.
Her life is gone. Anyone who declares that his life, for all intents and purposes, is now over, too, had better be 1000 percent sure of themselves. The question "What happened?" is, of course, natural. It was on all our lips. But the response cannot be found by pouring through old interviews Pistorius gave or from his now silent Twitter account. This is a murder investigation, not a guessing game. Serious stuff that needs to be treated as such.
At times like these, when a public figure we perhaps liked and admired is accused of things that are abhorrent, we want answers and we want them immediately.
We want to know not only the facts but what they mean, for us and the wider world. The first reaction is often shock. Then the questions: Does this mean we should also toss out everything we thought we knew about this person? If they were wrong'uns, was it also wrong to cheer for them, take pleasure in what they did and even be inspired by it?
In short, when our stars fall off the pedestals we build for them, we want to know not only whether we should burn their biographies, wristbands and commemorative T-shirts but also erase from our minds absolutely everything they said, did and supposedly stood for.
At the most basic level, one idea Pistorius promoted with his running was that facts speak for themselves.
Fact: A man whose lower legs were amputated when he was 11 months old can compete at the Olympics.
Fact: Pistorius changed attitudes when he made history at the London Games.
Fact: With each click-click-click of his prosthetic limbs on the track, he proved how wrong we can be when we make assumptions about people, when we try to guess what they are and aren't capable of.
Those are valuable lessons, especially now, when the lack of complete facts and pressure of so many questions can quickly lead to bum conclusions and answers.
Certainly, if Pistorius is found guilty of murdering Reeva Steenkamp, the lessons from London will not survive. Everything he achieved on the track would be rendered secondary. Police said Steenkamp was shot four times in Pistorius' villa Thursday. Prosecutor Gerrie Nel said in court he would pursue a charge of premeditated murder.
And if the charge doesn't stick? If there is another explanation? If, say, it was somehow an accident? How might we feel then? Too early to say.
His family issued a statement that said "the alleged murder is disputed in the strongest terms" - whatever that means.
A police spokeswoman, Brigadier Denise Beukes, said there previously were "allegations of a domestic nature" and "incidents" - whatever that means - at Pistorius' home.
"I'm not going to elaborate on it," Beukes said.
Too many questions and no answers. That shouldn't become an excuse to now speculate. It seemed inappropriate to be discussing matters so sad in 140 characters or less. But an ex-girlfriend of Pistorius made an important point on Twitter.
"All I am saying is let him speak, let his side be heard without jumping to conclusions," Jenna Edkins wrote.
Pistorius is in custody. We have not heard explanations from him. Instead, we're hearing from others, including journalists who spent time with him.
One wrote this week that Pistorius had "a sinister-looking machine gun" in his house. That isn't what the journalist wrote at the time of his visit in 2011. Then, it was simply "a machine gun." Already, the Pistorius narrative is being rewritten, when the full story is not yet known.
South Africa can be dangerous. The electrified fences on high walls around homes tell you that. Pistorius isn't the only South African to be armed. Nor is he the only 26-year-old who has professed to liking powerful motorbikes and driving at speed. Does that make him reckless, as some now suggest? Maybe. It certainly doesn't prove that he would commit murder.
Athletes often make poor role models. The sporting hall of infamy, the likes of Lance Armstrong, O.J. Simpson and Tiger Woods, long ago told us that.
Like most of us, star athletes don't broadcast if they beat their partners, abuse their kids, have substance problems, cheat, lie or are pathological. Unlike most of us, they also have sponsors who watch their backs and cover their tracks, PR agents who massage the message and lawyers to keep any ugly truth from getting out. So it always is a bigger shock when a carefully packaged athlete turns out to have been a rat or worse.
Pistorius was a carefully packaged athlete, with a story he told well.
What else he may also have been isn't yet clear.